[SI-LIST] Re: Question about split gnd planes
- From: "Leonard Dieguez" <ldieguez@xxxxxxxxxx>
- To: <etroy@xxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 25 May 2006 16:58:59 -0700
Ed,
I would try to not spilt the ground if you can. Many times you will
create more problems that fix. From your description you will be
creating a ground island. If it is excited it would probably radiate.
Also if you cross the ground with any signal traces either on top or
bottom of the ground split / island you may excite the ground through
inductive coupling and have a different reference with respect to the
rest of the ground. Since you have ground or power above or below the
island it will have a tendency to capacitive couple to the island any
noise in that area and could also excite the plane into resonance. If
you are worried about plane resonance you may try power/ground plane
termination simulations.=20
Leonard D.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Ed Troy
Sent: Thursday, May 25, 2006 1:39 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Question about split gnd planes
If you have a circuit board that requires a split gnd plane over a=20
small section of the board, and you have several ground planes,=20
should only one have the split (the one nearest the side containing=20
the components that require analog ground) while the rest of the=20
ground planes are continuous, or should the split section be on all=20
ground layers? I would think that you should only have it on one=20
layer. Also, if it should only be on one layer, I would imagine it=20
would be best to connect it to the digital ground with one, and only=20
one, via. Is that generally correct? What are some good references=20
for layer stackups, etc? I know I saw one, once, but can't remember
where.
Ed
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=20
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